1. Field of the Invention
The present invention relates to a pressure wheel device in a drive system for print medium in a printing machine. More particularly, the invention relates to such a device of the type comprising two pressure wheels mounted on respective support parts together with means for pressing each of the wheels against a respective edge of a print medium.
2. Description of the Prior Art
A field in which the invention is particularly, but not exclusively, applicable is printing or plotting machines in which a strip of paper or other printing media is moved by being pressed against a drive roller.
Devices of the above type are known in which each pressure wheel is associated with its own resilient device, and is optionally provided with an electrical or electromagnetic control for putting the wheel under pressure. In such known devices, it is practically impossible to equalize the pressure exerted by the pressure wheels on the print medium. The difference between the applied pressures of two or more wheels then may cause the print medium to slip in a zig-zag manner while being moved, thereby spoiling the printing being performed or the image being plotted.